LA 340 Intake Manifold

So what is the difference between an LA manifold and a magnum manifold and how can one manifold work for both applications if the ports are different or is it just the bolt pattern? Thanks.
So what is the difference between an LA manifold and a magnum manifold and how can one manifold work for both applications if the ports are different or is it just the bolt pattern? Thanks.
The LA attaching hardware is on an angle while the Magnum is straight up and down.

The he above intake pictured has both holes drilled/cast in to use on ether head. Port are close to the same. Problem is, port sizes vary slightly on every engine, every head, every year every casting series. An “X” head has a listed port size but you may find only 1 or 2 matching exactly that size on any single head never mind the run of millions.